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| author | bors <bors@rust-lang.org> | 2025-08-09 03:19:26 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2025-08-09 03:19:26 +0000 |
| commit | 2de2456fb7b2b55cb104bb03f30edd145c6015a3 (patch) | |
| tree | 0a7e1e293ad1b9e832d66bb9bcb2ebd6bab66d9d /compiler/rustc_middle | |
| parent | 4c7749e8c8e50ad146da599eea3a250160c1bc2b (diff) | |
| parent | 0bdaef5b63fe2d557483e72732e463b86ffb041b (diff) | |
| download | rust-2de2456fb7b2b55cb104bb03f30edd145c6015a3.tar.gz rust-2de2456fb7b2b55cb104bb03f30edd145c6015a3.zip | |
Auto merge of #143376 - dianne:guard-scope, r=matthewjasper
add a scope for `if let` guard temporaries and bindings This fixes my concern with `if let` guard drop order, namely that the guard's bindings and temporaries were being dropped after their arm's pattern's bindings, instead of before (https://github.com/rust-lang/rust/pull/141295#issuecomment-2968975596). The guard's bindings and temporaries now live in a new scope, which extends until (but not past) the end of the arm, guaranteeing they're dropped before the arm's pattern's bindings. This only introduces a new scope for match arms with guards. Perf results (https://github.com/rust-lang/rust/pull/143376#issuecomment-3034922617) seemed to indicate there wasn't a significant hit to introduce a new scope on all match arms, but guard patterns (rust-lang/rust#129967) will likely benefit from only adding new scopes when necessary (with some patterns requiring multiple nested scopes). Tracking issue for `if_let_guard`: rust-lang/rust#51114 Tests are adapted from examples by `@traviscross,` `@est31,` and myself on rust-lang/rust#141295.
Diffstat (limited to 'compiler/rustc_middle')
| -rw-r--r-- | compiler/rustc_middle/src/middle/region.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/rvalue_scopes.rs | 2 |
2 files changed, 7 insertions, 1 deletions
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs index 800c1af660a..857d041224f 100644 --- a/compiler/rustc_middle/src/middle/region.rs +++ b/compiler/rustc_middle/src/middle/region.rs @@ -96,6 +96,7 @@ impl fmt::Debug for Scope { ScopeData::Destruction => write!(fmt, "Destruction({:?})", self.local_id), ScopeData::IfThen => write!(fmt, "IfThen({:?})", self.local_id), ScopeData::IfThenRescope => write!(fmt, "IfThen[edition2024]({:?})", self.local_id), + ScopeData::MatchGuard => write!(fmt, "MatchGuard({:?})", self.local_id), ScopeData::Remainder(fsi) => write!( fmt, "Remainder {{ block: {:?}, first_statement_index: {}}}", @@ -131,6 +132,11 @@ pub enum ScopeData { /// whose lifetimes do not cross beyond this scope. IfThenRescope, + /// Scope of the condition and body of a match arm with a guard + /// Used for variables introduced in an if-let guard, + /// whose lifetimes do not cross beyond this scope. + MatchGuard, + /// Scope following a `let id = expr;` binding in a block. Remainder(FirstStatementIndex), } diff --git a/compiler/rustc_middle/src/ty/rvalue_scopes.rs b/compiler/rustc_middle/src/ty/rvalue_scopes.rs index 9bf6e3a7590..7dfe2d28051 100644 --- a/compiler/rustc_middle/src/ty/rvalue_scopes.rs +++ b/compiler/rustc_middle/src/ty/rvalue_scopes.rs @@ -44,7 +44,7 @@ impl RvalueScopes { debug!("temporary_scope({expr_id:?}) = {id:?} [enclosing]"); return (Some(id), backwards_incompatible); } - ScopeData::IfThenRescope => { + ScopeData::IfThenRescope | ScopeData::MatchGuard => { debug!("temporary_scope({expr_id:?}) = {p:?} [enclosing]"); return (Some(p), backwards_incompatible); } |